微乳胶粒的形成与表面活性剂的作用——粗粒化力场分子动力学模拟研究

从微观机理上研究表面活性剂对微乳胶粒形成的影响有利于推动微乳状液在各个领域的应用研究．本文采用分子动力学模拟方法研究了微乳胶粒的形成过程及表面活性剂对微乳胶粒形成的影响．正十二烷（C12H26）和十二烷基硫酸钠（SDS）作为油分子和表面活性剂分子的模型，Martini粗粒化（coarse．grained，CG）力场描述分子间和分子内的相互作用，对含有不同浓度的正十二烷和表面活性剂的12个模型分别进行了100ns的分子动力学模拟．模拟结果显示，不含表面活性剂的体系迅速发生水油相分离，且分离过程伴随着势能的明显下降；含有表面活性剂的体系中，在相同时间内通过模拟得到了稳定的、表面活性剂分子包裹油分子的胶粒．对不同温度下模拟得到的数据分析发现，胶粒形成初期的动力学特征可以近似地表达为二级反应，聚集活化能为14．6kJ／mol．

Formation of microemulsion particles with surfactant A coarse-grained molecular dynamics simulation study

It is of great interest to understand how surfactant molecules influence the formation of micro-emulsion particles in order to support application of microemulsions in various fields. In this paper, the effect of surfactants on the formation of microemulsion particles was studied using molecular dynamics simulations coupled with Martini force field, n-Dodecane （C12H26） and sodium dodecyl sulfate （SDS） were used as the models-representing oil and surfactant molecules respectively. Twelve simulation boxes containing C12H26 and SDS with different concentrations were used in simulations running for 100 ns. Simulation results showed that the phase separations occurred rapidly for systems without surfactants, and were accompanied with decreases of potential energies. For the systems with surfactants, stable oil particles covered by surfactants were observed in the same time. The initial kinetic characteristic of the formation of microemulsion particles can be expressed as the second order reaction approximately, and the activation energy is estimated to be 14.6 kJ/mol.